Chemical modification of bulk material substrates plays a central role in modern chemical, biological and material sciences, as well as in applied sciences, engineering and technology. Methods for chemical modification of bulk material substrates have developed by interfacial chemistry using organothiol-metals, enediol-oxides, silane-oxides, and other physicochemical methods, in which the predominant purpose is to impose desired properties on non-functional substrates. Molecules utilized for surface modification mostly have bifunctional end groups in which one end anchors to substrates and the other end provides chemical functionality to the substrate surface.
The existing toolbox for functional modification of material/substrate surfaces includes methods such as self-assembled monolayer (SAM) formation, functionalized silanes, Langmuir-Blodgett deposition, layer-by-layer assembly, and genetically-engineered surface-binding peptides. Although widely implemented in research, these conventional methods have limitations for widespread practical use. For instance, chemical specificity between interfacial modifiers and substrates (e.g., alkanethiols on noble metals and silanes on oxides) is typically required, complex instrumentation is typically required, and the substrate size/shape (Langmuir-Blodgett deposition) is often limited, or multi-step procedures for implementation (layer-by-layer assembly and surface-binding genetically engineered peptides) are required. More importantly, the substrates available for conventional surface modification chemistry is the primary limitation.
Mussel Adhesives
Mussels represent a natural surface-independent adhesive. Mussels are promiscuous fouling organisms which attach to virtually all types of inorganic and organic substrates, including classically adhesion-resistant materials such as polytetrafluoroethylene (PTFE) (FIG. 1A). Mussels' adhesive versatility may lie in the amino acid composition of proteins found near the plaque-substrate interface (FIG. 1B-D), which is rich in 3,4-dihydroxy-L-phenylalanine (DOPA) and lysine amino acids. DOPA participates in reactions leading to bulk solidification of the adhesive and forms strong covalent and non-covalent interactions with substrates.
Dopamine is a small molecule compound that contains both catechol (DOPA) and amine (lysine) groups (FIG. 1E). Dopamine can be electro-polymerized onto conducting substrates (Y. Li, et al., Thin Solid Films, 497, 270, 2006).
Needed in the art of surface modification is a method of surface-independent modification of a substrate whereby specific functional moieties can be displayed on the surface.
Biofouling Compositions
As long as ships have plied the seas, biofouling has had an overwhelming economic impact for the marine industry. Traditional antifouling paints containing biocides such as cuprous oxide in combination with one or more co-biocides are generally effective in reducing fouling of marine surfaces, although their use is associated with significant concerns related to their environmental impact on non-target aquatic species.
Tributyltin-containing paints were found to be effective in reducing biofouling. However, the application of tributyltin-containing paints is no longer permitted under a ban imposed by the International Maritime Organization (IMO) and more environmentally friendly approaches to fouling control are being actively sought. Commercial non-toxic alternatives to traditional biocidal antifouling paints have been silicone elastomers known as “fouling-release” coatings, which reduce the adhesion strength of marine organisms, facilitating their hydrodynamic removal at high speeds. These coatings, however, are expensive, not completely effective against all marine fouling including slimes, and do not release macrofouling from slow-moving vessels.
Therefore, the environmental and functional limitations of existing antifouling coatings highlight the need for new marine antifouling technologies.